786 research outputs found
Eternal Inflation with alpha'-Corrections
Higher-order alpha'-corrections are a generic feature of type IIB string
compactifications. In KKLT-like models of moduli stabilization they provide a
mechanism of breaking the no-scale structure of the volume modulus. We present
a model of inflation driven by the volume modulus of flux compactifications of
the type IIB superstring. Using the effects of gaugino condensation on
D7-branes and perturbative alpha'-corrections the volume modulus can be
stabilized in a scalar potential which simultaneously contains saddle points
providing slow-roll inflation with about 130 e-foldings. We can accommodate the
3-year WMAP data with a spectral index of density fluctuations n_s=0.93. Our
model allows for eternal inflation providing the initial conditions of
slow-roll inflation.Comment: 24 pages, 5 figures, LaTeX, v4: includes comparison with 3-year WMAP
data and values for the tensor ratio r and the running of n_
String Cosmology - Large-Field Inflation in String Theory
This is a short review of string cosmology. We wish to connect string-scale
physics as closely as possible to observables accessible to current or
near-future experiments. Our possible best hope to do so is a description of
inflation in string theory. The energy scale of inflation can be as high as
that of Grand Unification (GUT). If this is the case, this is the closest we
can possibly get in energy scales to string-scale physics. Hence, GUT-scale
inflation may be our best candidate phenomenon to preserve traces of
string-scale dynamics. Our chance to look for such traces is the primordial
gravitational wave, or tensor mode signal produced during inflation. For
GUT-scale inflation this is strong enough to be potentially visible as a B-mode
polarization of the cosmic microwave background (CMB). Moreover, a GUT-scale
inflation model has a trans-Planckian excursion of the inflaton scalar field
during the observable amount of inflation. Such large-field models of inflation
have a clear need for symmetry protection against quantum corrections. This
makes them ideal candidates for a description in a candidate fundamental theory
like string theory. At the same time the need of large-field inflation models
for UV completion makes them particularly susceptible to preserve imprints of
their string-scale dynamics in the inflationary observables, the spectral index
and the fractional tensor mode power . Hence, we will focus this
review on axion monodromy inflation as a mechanism of large-field inflation in
string theory.Comment: 34 pages, 1 figure, LaTeX, v2: typos fixed, 3 references added,
agrees with published version in "Perspectives in String Phenomenology" and
"International Journal of Modern Physics A
Moduli Stabilization in Meta-Stable Heterotic Supergravity Vacua
We revisit the issue of moduli stabilization in a class of N=1 four
dimensional supergravity theories which are low energy descriptions of standard
perturbative heterotic string vacua compactified on Calabi-Yau spaces. In
particular, we show how it is possible to stabilize the universal dilaton and
Kahler moduli in a de Sitter/Minkowski vacuum with low energy supersymmetry
breaking by means of non-perturbative gauge dynamics, including recent results
by Intriligator, Seiberg and Shih. The non-SUSY vacua are meta-stable but
sufficiently long-lived.Comment: 1+31 pages, LaTeX, uses JHEP3 class, v2: references corrected and
added, version published in JHE
Non-Equilibrium Random Matrix Theory : Transition Probabilities
In this letter we present an analytic method for calculating the transition
probability between two random Gaussian matrices with given eigenvalue spectra
in the context of Dyson Brownian motion. We show that in the Coulomb gas
language, in large limit, memory of the initial state is preserved in the
form of a universal linear potential acting on the eigenvalues. We compute the
likelihood of any given transition as a function of time, showing that as
memory of the initial state is lost, transition probabilities converge to those
of the static ensemble.Comment: REVTeX, 5 pages, 2 figure
Inflation with a graceful exit in a random landscape
We develop a stochastic description of small-field inflationary histories
with a graceful exit in a random potential whose Hessian is a Gaussian random
matrix as a model of the unstructured part of the string landscape. The
dynamical evolution in such a random potential from a small-field inflation
region towards a viable late-time de Sitter (dS) minimum maps to the dynamics
of Dyson Brownian motion describing the relaxation of non-equilibrium
eigenvalue spectra in random matrix theory. We analytically compute the
relaxation probability in a saddle point approximation of the partition
function of the eigenvalue distribution of the Wigner ensemble describing the
mass matrices of the critical points. When applied to small-field inflation in
the landscape, this leads to an exponentially strong bias against small-field
ranges and an upper bound on the number of light fields
participating during inflation from the non-observation of negative spatial
curvature.Comment: Published versio
Chaotic Inflation in Supergravity after Planck and BICEP2
We discuss the general structure and observational consequences of some of
the simplest versions of chaotic inflation in supergravity in relation to the
data by Planck 2013 and BICEP2. We show that minimal modifications to the
simplest quadratic potential are sufficient to provide a controllable tensor
mode signal and a suppression of CMB power at large angular scales.Comment: 13 pages, 6 figures, minor references change
Higher-Derivative Supergravity and Moduli Stabilization
We review the ghost-free four-derivative terms for chiral superfields in
supersymmetry and supergravity. These terms induce cubic
polynomial equations of motion for the chiral auxiliary fields and correct the
scalar potential. We discuss the different solutions and argue that only one of
them is consistent with the principles of effective field theory. Special
attention is paid to the corrections along flat directions which can be
stabilized or destabilized by the higher-derivative terms. We then compute
these higher-derivative terms explicitly for the type IIB string compactified
on a Calabi-Yau orientifold with fluxes via Kaluza-Klein reducing the
corrections in ten dimensions for the respective
K\"{a}hler moduli sector. We prove that together with flux and
the known -corrections the higher-derivative term stabilizes all
Calabi-Yau manifolds with positive Euler number, provided the sign of the new
correction is negative.Comment: Latex, 44+1 pages; v2: References and comments added; estimates of
scales added to sec. 4.
Moduli stabilization and SUSY breaking in heterotic orbifold string models
In this paper we discuss the issues of supersymmetry breaking and moduli
stabilization within the context of E_8 x E_8 heterotic orbifold constructions
and, in particular, we focus on the class of "mini-landscape" models. In the
supersymmetric limit, these models admit an effective low energy field theory
with a spectrum of states and dimensionless gauge and Yukawa couplings very
much like that of the MSSM. These theories contain a non-Abelian hidden gauge
sector which generates a non-perturbative superpotential leading to
supersymmetry breaking and moduli stabilization. We demonstrate this effect in
a simple model which contains many of the features of the more general
construction. In addition, we argue that once supersymmetry is broken in a
restricted sector of the theory, then all moduli are stabilized by supergravity
effects. Finally, we obtain the low energy superparticle spectrum resulting
from this simple model.Comment: LaTeX, v2: 57+1 pages, 4 figures, 8 Tables, added references; this
version i) discusses volume moduli stabilization with exponentials of both
sign (as sometimes mandated by modular invariance); ii) includes the
anomalous U(1)_A D-term & the leading Coleman-Weinberg 1-loop correction into
the MSSM soft masses to prevent tachyonic results
On uplifts by warped anti-D3-branes
In this note we outline the arguments against the ten-dimensional consistency
of the simplest types of KKLT de Sitter vacua, as given in arXiv:1707.08678. We
comment on parametrization proposals within four-dimensional supergravity and
express our disagreement with the recent criticism by the authors of
arXiv:1808.09428.Comment: Latex, revtex, 4 pages, 1 figure, v2: references added, minor
clarification
- …